Security cards are widely used for various applications such as identification purposes (ID cards) or financial transfers (credit cards). Such cards typically consist of a laminated structure consisting of various plastic lamellae and layers wherein one or more of them carry information, e.g. alphanumeric information, logos, a picture of the card holder, etc.
Writable cards wherein the user can store digital information are also known, e.g. cards comprising a magnetic strip, optically recordable cards or cards comprising an electronic chip, sometimes called ‘smart cards’.
A principal objective of security cards is that it cannot be easily modified or reproduced in such a way that the modification or reproduction is difficult to distinguish from the original. Therefore security features, e.g. a hologram, are usually positioned on the front or the back of a security card, rather than on the thin edge.
WO 2008/110892 (SETEC) discloses an identification document comprising at least two constitution layers, wherein at least one edge of the identification document is marked with written data that are etched into the edge by means of a laser beam. The written data overlap with constitution layers, in order to prevent a fraudulent delamination of the document. Such laser marking involves the carbonization of material, e.g. polycarbonate, whereby the colour of the written data is always black. Hence, it is not possible to provide data marked in a colour different from black on the edge of the identification document.
Coloured markings on the edge of a security card can be provided by printing techniques such as, for example, inkjet printing. US 2005087606 A (DATACARD) discloses a card having non-visible or visible communication markings printed on the perimeter edge surface of the card using an ink-jet printer. The markings, e.g. lines of a barcode, are generally printed on the perimeter edge surface in a direction perpendicular on the longest side of the perimeter edge. It is very difficult to print a long straight line parallel with the longest side of the perimeter edge surface. Furthermore, the communication markings on the perimeter edge surface tend to suffer from wear and tear.
US 2009187435 discloses driver's licenses and other security documents including one or more machine-readable features which are encoded around the entire edge of the card using printing or laser engraving. Paragraphs [0090] to [0093] disclose that physical voids having a long lifetime may be created into the edge surface by laser engraving in order to increase the durability of the marking. These voids, penetrating the perimeter edge surface, may be filled with ink, or not.
DE 10 2007 037 982 A1 (Bundesdruckerei) and U.S. Pat. No. 6,328,342 disclose security documents having holes in the middle of a lamella, which can be filled with a colorant, but are only visible from the front or backside and not from the side.
Since methods for falsification and counterfeiting of security documents continue to develop and improve, it remains a constant battle to protect security documents against falsification and counterfeiting. Therefore a need exists to provide simple and cost-effective methods for securing documents. It would be desirable to be able to provide text matter in a different colour than black on the perimeter edge surface, which also does not suffer from wear and tear.